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Comparative in vitro activity of doxycycline and oxytetracycline against porcine respiratory pathogens
Author(s) -
Bousquet E.,
Morvan H.,
Aitken I.,
Morgan J. H.
Publication year - 1997
Publication title -
veterinary record
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.261
H-Index - 99
eISSN - 2042-7670
pISSN - 0042-4900
DOI - 10.1136/vr.141.2.37
Subject(s) - oxytetracycline , pasteurella multocida , microbiology and biotechnology , mycoplasma hyopneumoniae , doxycycline , actinobacillus pleuropneumoniae , minimum inhibitory concentration , biology , florfenicol , serial dilution , agar dilution , antibiotics , bacteria , medicine , serotype , genetics , alternative medicine , pathology
Minimum inhibitory concentrations of doxycycline and oxytetracycline were determined against 55 Pasteurella multocida strains, 59 Actinobacillus pleuropneumoniae strains and 26 Mycoplasma hyopneumoniae strains isolated from the respiratory tract of pigs. An additional set of 76 P multocida strains isolated from pneumonic pigs was tested for their minimum inhibitory concentrations of doxycycline. The P multocida and A pleuropneumoniae strains were isolated in France and the minimum inhibitory concentrations were determined by an agar dilution method. The M hyopneumoniae strains were isolated in the United Kingdom and minimum inhibitory concentrations were determined by a serial broth dilution method. All the strains tested were susceptible to doxycycline whereas 15 per cent of the P multocida strains and 22 per cent of the A pleuropneumoniae strains were resistant to oxytetracycline. Doxycycline concentrations inhibiting 90 per cent of strains were 1 μg/ml for P multocida and 2 μg/ml for A pleuropneumoniae . The ratio of the minimum inhibitory concentrations of doxycycline and oxytetracycline ranged between 1/1 and 1/4 for the oxytetracycline‐susceptible strains and between 1/16 and 1/64 for the oxytetracycline‐resistant strains. All the M hyopneumoniae strains were susceptible to doxycycline and oxytetracycline, the concentrations inhibiting 90 per cent of strains being 1 μg/ml and 2 μg/ml, respectively. These data confirm that doxycycline has a higher in vitro activity against pig respiratory pathogens than oxytetracycline.